1. Field of the Invention
The present invention relates generally to media storage libraries and more specifically to the movement of robotic mechanisms within the library.
2. Background of the Invention
Typical storage library designs using more than one picker robot have contention problems. For example, when one robot is moving toward a tape reader unit another robot will want to move away from the unit, and their paths must meet somewhere. This is especially likely when two robots are moving in opposite directions on the same guide rail or track. This contention between robots effectively causes performance degradation and makes the control of the robots extremely complex. Special control software is needed to coordinate robot movements in order to avoid contention between robots on the same track.
Therefore, it would be desirable to have a method for avoiding robot contention on guide rails, without the need of complex robot coordination and increased software complexity.
The present invention provides a system for directing robot movement in a storage library, the library comprising at least one horizontal array of storage cells and at least one robot that moves along the horizontal array and can retrieve objects from and place objects into the storage cells. The system comprises a guide rail that runs along the length of the horizontal array and loops around from one end of the horizontal array to the other end. The robot may move along the guide rail in a continuous, unidirectional loop. If multiple robots are added to the library, they can be made to move in the same direction along looping guide rail, thus elimination contention among robot movements. If multiple horizontal arrays are stacked vertically within the library, the looping guide rail allows robots to loop around and return to the same level or move onto a different horizontal level.